Update to Johnson 1987 88hp SPL running problem

jerryny

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Let me start by apologizing for not providing the whole story on the problem on the trouble I am having with my 1987 Johnson V4 88hp SPL. I am proving the whole history now along with some results from tests I did this morning. I also want to apologize for starting a new thread but I didn't seem to be getting any responses after providing the the whole story yesterday. I thought maybe it was too far down in the forum. Anyways here is the story:

Last fall my son bought the boat and it wasn't running right so he gave up and gave it to me. The original problem was that the engine would run fine all the time at idle. But once you put it in gear it would lose all power after about 5 minutes and never regain it till the next time you went out and then the same thing would happen. So here is what I did and found:

1) Replaced fuel pump. It was a cheap shot at solving the problem. The problem still existed.
2) Rebuilt carbs. Didn't help
3) Did both a warm and cold compression test. If I remember right all 4 cylinders were about 135lbs.
4) Did a spark plug gap test on all 4 cylinders. All 4 had a nice blue spark that jumped the gap.

By now it was winter so I decided to replace the deck which was soft in a few spots. Its at this time that I found that the vent line for the inboard gas tank was bloated and falling apart. So I replaced the vent line and waited for spring.

This spring I took it out and it ran like a champ. I have had it out at least 4 or 5 times and it always ran great until this last weekend when it started acting up and had no power when in gear.

So while I was out on the river I did the following:

1) Removed vent line from gas tank but no difference which I kinda already knew.

2) I put a spark plug monitor on each of the two top plugs since they were the ones that were wet.
It was pretty bright out so I put my hat over the tester and I could see that the light was pulsing on both top
cylinders. (didn't check the bottom two cylinders since the plugs were a brownish color and dry)

3) I then took the carb cover off to look at them while the engine was running. I could see gas flowing into the carbs.
Not sure if this is good or bad. I did see some white greasy substance on the bottom of what I think they call air
horns. The choke plates and the rest of what I could see were nice and shiny.

I then brought the boat in. Here are my plans for shooting the problem. Please let me know if I'm doing the right steps in the right order:

- Gonna redo the compression test just for sanity's sake. 135lbs on all 4 cylinders with engine warm

- Redo the spark gap test again just to make sure all 4 coils and 2 power paks are still working. All 4 coils were putting out a nice blue spark and had no trouble jumping a 1/2 inch gap

- Ran engine with inline spark plug testers All 4 testers were lighting up as the engine ran

- So I guess all that leaves is to pull the top carb and check the jets and make sure the float isn't sticking and blow it all out.

- The white greasy substance on the bottom of what I think they call air horns has me puzzled. Never saw that on the last Johnson motor I had which was a 1972 50hp 2 cylinder.


Am I missing something or is this the right way to precede? I want to thank all that reply. This is so frustrating.

Jerry
 

fireman57

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Re: Update to Johnson 1987 88hp SPL running problem

I don't know what you are calling the air horns but I am guessing that is the carb throats. After running you will have some white stuff on them as they run very cold and you will have condensation mixing with some fuel there.
 

jerryny

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Re: Update to Johnson 1987 88hp SPL running problem

I don't know what you are calling the air horns but I am guessing that is the carb throats. After running you will have some white stuff on them as they run very cold and you will have condensation mixing with some fuel there.
Yes its the carb throats I am talking about. Thanks
 

emdsapmgr

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Re: Update to Johnson 1987 88hp SPL running problem

You've done some nice analysis. A logical approach, too. Would be interesting to do a cyl drop test once the engine is well warmed up. Heat is the enemy of weak ignition components. It may run fine when cold, then act up when it warms up. Once the engine starts to act up, put the engine in neutral and pull one spark plug wire off. Normally, the engine's rpm will drop, indicating it's only running on 3 cyls. Replace the wire and pull the next plugwire off the next plug. Repeat with all 4 plugwires. You should get the same results. If you pull one wire off and nothing happens, the plug is probably not firing (contributing to running the engine..) Regarding the white substance, that could indicate water intrusion into the engine. You've described the white greasy substance, and that's about what water mixed with oil/fuel looks like. This could come from a leaky exhaust gasket and usually affects either of the lower two cyls. After running, see if you can see anything inside the cyl with a pencil light.
 

jerryny

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Re: Update to Johnson 1987 88hp SPL running problem

Ok I was finally able to get the boat out on the water to do some more trouble shooting.

1) I hooked up a separate 5 gal gas tank to see if the problem is being caused by the inboard gas tank. Made no difference

2)I removed the cover off the 2 carbs. I then put it in gear and advanced the throttle until it bogged down. At this point I sprayed gas into the upper carb. No difference
Next I sprayed some gas into the bottom carb and the boat immediately surged forward like it should. I waited until the engine bogged down again and then repeated the test. Same results. Spraying gas into the lower carb makes the engine run 100% better.

So I am going to assume that I need to clean out the bottom carb.

Anyone think this is the wrong approach.

Thanks
Jerry
 

rothfm

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Sep 26, 2006
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Re: Update to Johnson 1987 88hp SPL running problem

Nope....Good approach. That certainly tells you something. Probably need to pull apart that carb (fully) to clean. Also take a close look at those lines and hoses. Sounds like you are right there.
 

emdsapmgr

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Re: Update to Johnson 1987 88hp SPL running problem

Once you get the lower carb off, I'd pull the jets out. Esp the two high speed jets. Visually inspect them for any debris, restriction, such as black fuel hose particles. That carb also has an idle jet and a mid-jet. If that lower carb is running lean on fuel, it is also running lean on oil. Best to resolve this before the lean condition causes other problems.
 

fireman57

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Aug 24, 2004
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Re: Update to Johnson 1987 88hp SPL running problem

emdsapmgr is right on the oil. Better make sure you have fuel going into that cylinder. Like my dad used to say about his car: The generator don't gen, and the carbeurator don't carb, and the pistons, well they don't work either.
 

TD_Maker

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Aug 31, 2005
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Re: Update to Johnson 1987 88hp SPL running problem

Did you change out the Carb gaskets (the ones between the carb and the intake) when you rebuilt the carbs? A torn or ripped gasket will allow the carb to suck too much air.
 

jerryny

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Re: Update to Johnson 1987 88hp SPL running problem

Ok got the carbs off and disassembled. All jets look clean. I did however find some crap in the float bowl. It was reddish and flat. Almost looked like old gasket material. But the gaskets are black and brown and seems as though they are made either of rubber or silicone.
Anyways, going to clean everything out and put em back together and hopefully I can get out on the water tomorrow and see what happens.
 

fireman57

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Re: Update to Johnson 1987 88hp SPL running problem

Let us know what happens either way.
 

jerryny

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Re: Update to Johnson 1987 88hp SPL running problem

out of curiosity how to I tell if i have an early or late production of the carbs that r on my Johnson 87 88 hp SPL engine. I just asking because the parts guide list 2 different part numbers for the intermediate ORIFICE which I am assuming they mean jets. From looking at the part that came out of the carb it looks like the early production version of the jet. Thanks everyone for your help. This is the greatest place for help for a newbie. I've learned so much with all your guys help.
 

fireman57

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Re: Update to Johnson 1987 88hp SPL running problem

I don't know how to tell the difference in the jets, which are the same as orafices, but if it ran fine at one time for the original owner I would assume that they are the correct ones. You can always replace them for not much money and see if the other ones work better. You will need to buy or make a special screwdriver to get the high speed jets out though. I just ground down a regualr screwdriver to fit.
 

emdsapmgr

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Re: Update to Johnson 1987 88hp SPL running problem

Each jet is stamped on it's side with it's size. Both jets for the mids are the same size. What is different about them is the thread size as you screw it into the carb. This is about the time that OMC switched from aluminum carb bowls to the plastic ones. During that switch, they changed the thread size on the mid jet hole. So, even though they flow the same fuel, they have different threads. The 333459 jet has a 1/4 20 thread size. The 324652 is an 8/32" thread size. Hopefully you have the aluminum bowls. They are the best. If you have plastic bowls, they tend to warp with age and are prone to leaking. If warped in a certain way, they actually can ingest air into the carb, causing it to run lean. Personally, I would not run the plastic carb bowls.
 

fireman57

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Re: Update to Johnson 1987 88hp SPL running problem

Emd that is some great info. Thanks for the save.Never would have thought they would change thread size.
 

jerryny

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Re: Update to Johnson 1987 88hp SPL running problem

Got carbs all cleaned out, put back together and on the engine. Took boat out this morning and it ran great. I alternated between full speed then slowing down for a while and then opening her back wide open. Did this for about 45 mins and it performed great. Thanks to everyone for all their help and advice. Hoping to be able to have fun for the rest of the summer. I just knocked on a giant piece of oak. l
:joyous:
Jerry
 

fireman57

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Re: Update to Johnson 1987 88hp SPL running problem

Glad to hear it. Amazing what a proper carb douching accomplishes. Enjoy what is left of the summer.
 
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